Fluorescent fiber, its use and processes for its production

ABSTRACT

The present invention relates to a regenerated cellulosic fiber which contains an incorporated dye pigment and a fluorescent dye applied by overdying, the use of this fiber for the production of yarns and fabrics and a process for the production of these fibers. This fiber satisfies the demands of EN 471 in relation to luminance factor, the chromaticity coordinates and color fastness and possesses a light fastness (ISO 105-B02, process 2) of more than 5.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject-matter of the present invention is cellulosic regenerated fibers with fluorescent properties for applications in reflective clothing such as is for example described in standard EN 471, their use for the production of yarns and fabrics and a process for the production of these fibers.

2. State of the Art

EN 471 deals exclusively with the warning effect of personal protective equipment, particularly with reflective clothing. As a rule protective clothing comprises a fluorescent background material and a retro-reflective material. For the purpose of the present invention, a material is designated as a fluorescent material in accordance with the definition in EN 471 which emits radiation at a longer wave length rather than absorbs it; in the further text, the term High-Vis-Material is used for this. The present invention refers to the fluorescent background material but not to retro-reflective materials.

Until now High-Vis-textiles were mainly produced on the basis of synthetic fibers and in particular polyester, which, however, reveal disadvantages with regard to the wear comfort and safety. The disadvantages of textiles like this lie in particular in their unpleasant skin climate and in the development of smell after being worn for a longer period of time due to insufficient moisture-regulating material properties, as well as in the danger of electrostatic charging typical for synthetic fibers.

Complex textile structures represent an alternative, the outer side of which contains the High-Vis-component and the inner side of which mainly comprises cellulosic fibers to improve the wear comfort, such as for example is described in WO 2006/017709. Today above all fibers according to the viscose process and Lyocell process are known as cellulosic regenerated fibers. These are produced around the world for standard applications in the textile and nonwovens sector with an individual fiber titer of between 0.8 and 16 dtex.

Cellulosic regenerated fibers can indeed be dyed using the conventional bath dyeing process with fluorescent dyestuffs. However, the fibers dyed in this way do not satisfy the requirements for light fastness (ISO 105-B02, process 2>5). Following xenon radiation, they are considerably faded and their shade reveals a considerable change. Moreover, the depth of color is greatly reduced which can for example be identified as a shifting of the chromaticity coordinates.

For decades it has been known that viscose fibers can be dyed in a permanent manner by incorporating dye pigments. Corresponding fibers are available in the market. Until now, however, no spun-dyed cellulosic regenerated fibers which comply with the requirements of EN 471 are available.

SUMMARY OF THE INVENTION Assignment of Task

Compared to this state of the art, the task was to make a fiber available which on the one hand satisfies the requirements made in terms of protective and reflective clothing, as is for example described in EN 471 and on the other hand, the wear comfort and safety aspects of this clothing with a justifiable economic expenditure. For this reason it should be possible to produce the protective and reflective clothing from a fiber like this without the addition of any other types of fibers. In this respect it is particularly important that the textiles made of these fibers pass the following requirements for background materials in accordance with EN 471:

Luminance factor (standard values according to CIE Publication No. 15.2) and chromaticity coordinates

Color after xenon radiation: the exposure of the sample takes place according to ISO 105-B02, process 3

Rub fastness dry and wet (ISO 105-A02)

In addition the light fastness of the fibers is determined in accordance with ISO 105-B02, process 2.

Furthermore the task was to make a suitable production process available for these fibers.

DETAILED DESCRIPTION OF THE INVENTION

Surprisingly it was possible to solve this task using cellulosic regenerated fibers, which contain an incorporated dye pigment and a fluorescent dye applied as a result of overdying. These fibers in accordance with the invention reveal a light fastness—measured in accordance with ISO 105-B02, process 2—of more than 5 in addition to the enhanced wear comfort and increased safety due to the basic cellulosic structure. It was not possible to realize this with the cellulosic fibers known until now.

The fibers also satisfy the other values demanded in EN 471 with regard to the rub fastness, fastness to perspiration, fastness to washing, dry cleaning fastness, fastness to hypochlorite bleach and ironing fastness.

The spun-dyed cellulosic regenerated fiber can be produced using a viscose process, a modified viscose process (e.g. a Modal process, a zinc-free viscose process with Al-sulfate, etc.), as well as a solvent process which works with organic solvents such as melted aqueous amine oxides or also so-called ionic liquids. The fibers can be correspondingly designated as Viscose, Modal and/or Lyocell.

The cellulosic regenerated fiber can contain other additives. In one preferred embodiment of the invention, the cellulosic regenerated fiber is, in addition, equipped with a flame-resistant agent.

One preferred embodiment of the flame-resistant fiber is produced by incorporating a pigment-shaped flame-resistant agent. Besides other types, in particular organophosphorus compounds can be considered as pigment-shaped flame-resistant agents, for viscose for example the well suited and well-known 2,2′-Oxybis[5,5-dimethyl-1,3,2-dioxaphosphorinan]2,2′disulfid, available under the commercial names of Exolit® or Sandoflam®.

In one other preferred embodiment of the invention, the cellulosic regenerated fiber is also equipped with an anti-bacterial agent. In this respect the substances known to the expert can be used.

The subsequent High-Vis-bath dyeing can be carried out with dyestuffs suitable for cellulosic materials (e.g. reactive dyestuffs, direct dyestuffs, vat dyes, etc.).

The overdying, i.e. the bath dyeing, can either be performed in the flock of the spun-dyed fiber, in a yarn which contains the spun-dyed fiber or in a fabric which contains the spun-dyed fiber. In this respect basically the continuous and discontinuous dyeing processes known to the expert can be used.

By selecting the pigment in a suitable manner for spin-dyeing and the High-Vis-dyestuff for bath dyeing, shades of color can be obtained for which there were until now no individual solutions.

The subject-matter of the present invention is also the use of the fiber in accordance with the invention for the production of a yarn. To feature properties suitable for the respective scope of application, a yarn like this in accordance with the invention can also contain fibers of another origin in addition to the fibers in accordance with the invention, for example (flame-resistant) polyester, Modacryl, para- and meta-Aramide, polyamidimide (Kermel®), (flame-resistant) wool, polybenzimidazole (PBI), polyimide (P84®), polyamide, (flame-resistant) polyamide, flame-resistant acrylic fibers, melamine fibers, polyphenylensulfide (PPS), polytetrafluorethylene (PTFE), glass fibers, cotton, silk, carbon fibers, oxidized thermally stabilized polyacrylnitrile fibers (PANOX®) and electrically conductive fibers, as well as blends of these fibers. In one preferred embodiment of the invention, the blending partners can likewise reveal a High-Vis-finish.

Likewise the use of fibers in accordance with the invention for the production of a fabric is the subject matter of this invention. Apart from the fibers in accordance with the invention, this fabric can also contain other fibers, for example (flame-resistant) polyester, Modacryl, para- and meta-aramide, Polyamidimide (Kermel®), (flame-resistant) wool, polybenzimidazole (PBI), polyimide (P84®), polyamide, (flame-resistant) polyamide, flame-resistant acrylic fibers, melamine fibers, polyphenylensulfide (PPS), polytetrafluorethylene (PTFE), glass fibers, cotton, silk, carbon fibers, oxidized thermally stabilized polyacrylnitril fibers (PANOX®) and electrically conductive fibers, and blends of these fibers. In one preferred embodiment of the invention, the other fibers can also feature a High-Vis-finish.

The fabric is preferably a woven, warped or knitted fabric, but can also basically be a non-woven. In the event of a woven or knitted fabric, the blend of fibers in accordance with the invention with the other fibers is possible either by blending prior to yarn production, a so-called intimate blend, or by the joint use of in each case pure yarns of the different types of fibers when weaving, warping or knitting.

In the same way the subject-matter of the present invention is also the use of fibers in accordance with the invention for the production of a reflective article of clothing or another kind of reflective article whereby normally the above-named yarns and/or planar textile structures appear as intermediate steps within the textile chain. For the purposes of this invention as other kinds of reflective articles shall be understood for example streamers, flags, warning bands and the like, which show a particularly high visibility and/or attract a great deal of attention. The use according to this invention therefore goes beyond a pure warning effect. If as a fabric a nonwoven fabric—as mentioned above already—is used, e.g. for the use in streamers, flags, warning bands and the like, then of course the intermediate yarn does not apply. Different embodiments of articles of clothing or of other reflective articles of this kind are well known to the specialist and do not, therefore, need to be described any further.

Likewise a process for the production of the above-named fluorescent, cellulosic regenerated fibers in accordance with the invention is also the subject-matter of the present invention, in which a dye pigment is incorporated into the fibers and these fibers are overdyed with a fluorescent dyestuff in a later process step.

The incorporation is normally performed by adding dye pigments to the spinning solution. Incorporation processes of this kind are basically known to the specialist both for the viscose, Modal and the solvent spinning process. However, spun-dyed cellulosic fibers are normally not overdyed in another step with another dyestuff since the spin-dyeing process is known generally as a very effective process with which high fastness values, as well as rub and light fastness, fastness to washing and perspiration can be attained. However, the present invention, which is the combination with an overdying step at a later stage, fulfils the special demands of fibers of cellulose for reflective clothing.

The overdying, i.e. bath dying, can take place either in the flock, which contains the spun-dyed fibers or on a yarn or a textile structure which contains the spun-dyed fibers. In this respect the continuous and discontinuous dyeing processes generally known to the specialist can be used.

The invention will now be explained by means of example. These are to be understood as possible embodiments of the invention. In no way is the invention restricted to the scope of these examples.

Example 1

A spun-dyed flame-resistant viscose fiber contains 1.25 weight percentage of a pigment yellow 3 (e.g. Aquarine Yellow 10 G) and 22 weight percentage 2,2′-Oxybis[5,5-dimethyl-1,3,2-dioxaphosphorinan]2,2′disulfid (Exolit 5060, Messrs. Clariant) always in relation to cellulose. This fiber is then overdyed with Remazol Leuchtgelb FL (Messrs. DyStar) according to the following recipe:

The flock is placed in a dye bath, containing 2% Remazol Leuchtgelb FL (Messrs. DyStar) and 100 g/l sodium sulphate with a liquor ratio of: 1:10 and a starting temperature of 25° C. and with a heating rate of 1° C./min to 50° C. After 10 min at this temperature, 5 g/l of soda is added and after another 30 min 1.2 ml/l NaOH (containing 50%). After another 40 min, the dyeing bath is allowed to cool down and then a post-treatment follows with the steps known to the specialist of rinsing-soaping-rinsing-soaping.

The fiber was then dried and a woven fabric made out of this. This produced the test results contained in table 1. These results show that the fibers, yarns and textiles produced in accordance with the invention are excellent for use in reflective clothing and do not fade.

TABLE 1 test results (for example 1) After exposure (ISO 105-B02, Start process 3) Luminance factor 0.7304 0.7282 chromaticity X coordinate 0.3830 0.3852 coordinates Y coordinate 0.4917 0.4915 Rub fastness (wet and dry) 4 Light Fastness (ISO 105-B02 process 2) 5-6

Example 2 Comparative Example

A commercially available viscose fiber (LENZING FR), also rendered flame-resistant with Exolit 5060 which contained no incorporated dye pigment, was overdyed using the same method as in example 1. In this respect 6% Remazol Leuchtgelb FL (Messrs. DyStar) was used instead of 2% as in example 1. The fiber revealed the test results contained in table 2.

TABLE 2 test results (for example 2) After exposure (ISO 105-B02, Start process 3) Luminance factor 0.7666 0.7011 Chromaticity X coordinate 0.3711 0.3920 coordinates Y coordinate 0.5184 0.5067 Rub fastness (wet and dry) 4 Light Fastness (ISO 105-B02 process 2) 3-4

As a result of exposure, the shade and depth of color of the fiber according to the state of the art in example 2 changed much more strongly than that of the fiber in accordance with the invention from example 1, which can also be clearly recognized in the strong shift in the coordinates of the chromaticity coordinates. Likewise the luminance factor deteriorates in the fiber not in accordance with the invention as a result of exposure much more strongly than in the fiber in accordance with the invention. However, the much worse light fastness of the fiber in example 2, compared to the fiber in accordance with the invention of example 1, is particularly grave. 

1. A cellulosic regenerated fiber comprising an incorporated dye pigment and a fluorescent dyestuff wherein the fluorescent dyestuff is applied by overdying.
 2. The cellulosic regenerated fiber according to claim 1, wherein said fiber has a light fastness, measured according to ISO 105-B02, process 2, of more than
 5. 3. The cellulosic regenerated fibers according to claim 1, wherein said fiber is produced according to the Viscose, Modal or Lyocell process.
 4. The cellulosic regenerated fiber according to claim 1, wherein said fiber is finished in a flame-resistant manner.
 5. The cellulosic regenerated fiber according to claim 4, wherein the flame-resistant finish is an incorporated organophosphorus compound.
 6. The cellulosic regenerated fiber according to claim 1, further comprising an antibacterial agent.
 7. A yarn comprising the fibers according to claim 1, 2, 3, 4, 5, or
 6. 8. A fabric comprising the fibers according to claim 1, 2, 3, 4, 5, or
 6. 9. A reflective article comprising the fibers according to claim 1, 2, 3, 4, 5, or
 6. 10. A process for the production of a fluorescent cellulosic regenerated fibers according to claim 1, 2, 3, 4, 5, or 6, comprising incorporating a dye pigment into the fibers and overdying the fibers with a fluorescent dyestuff in a later process step.
 11. The process according to claim 10, wherein the overdying is performed in a continuous or discontinuous process step.
 12. The process according to claim 10, wherein the overdying is performed on a yarn or fabric made from the regenerated cellulosic fiber.
 13. The cellulosic regenerated fiber according to claim 5, wherein the organophosphorus compound is 2,2′-Oxybis[5,5-dimethyl-1,3,2-dioxaphosphorinan]2,2′disulfid.
 14. The reflective article according to claim 9, wherein said article is clothing. 